Both menopause and imbalances in cervicovaginal (CV) microbial communities are associated with increased risk of HIV-1 acquisition. Recent studies indicate that postmenopausal women exhibit elevated abundances of CD4+ T-lymphocytes expressing C-C chemokine receptor type 5 (CCR5), a HIV-1 coreceptor. Because low estrogen, as occurs following menopause, is linked to distinct alterations in the CV microbiota, our primary objective is to determine whether commensal CV microbial communities mediate the association between menopause and elevated populations of CCR5+CD4+ T-cells in the female reproductive tract. We hypothesize that menopause-dependent suppression of innate mucosal immune function alters the types and quantities of microbes and microbial products to which the cervicovaginal mucosa is exposed. The resulting increased burden of novel microbial antigens is further hypothesized to compromise cervical immune homeostasis, thereby increasing recruitment of HIV-1 target cells to the cervical sub-mucosa. These hypotheses will be tested using high-throughput, metagenomic analysis of CV lavage and cervical tissue specimens in order to accomplish the following specific aims: Aim 1. Determine whether an altered composition of the cervicovaginal microbiota is associated with elevated levels of CD4+ T-lymphocytes expressing chemokine coreceptors (e.g., CCR5, CXCR4) or activation markers (e.g., HLA-DR, CD38). Aim 2. Determine whether menopause is associated with altered densities of bacteria in proximity to the cervical epithelium. Aim 3. Determine whether gene expression patterns of cervical mucosal epithelia and resident microbiota differ in a comparison of premenopausal and postmenopausal women. PUBLIC HEALTH RELEVANCE: Both menopause and imbalances in the bacterial communities normally inhabiting the female reproductive tract are associated with increased risk of HIV-1 acquisition. Recent studies indicate that postmenopausal women exhibit elevated abundances of immune cells (certain T-lymphocytes) that are susceptible to HIV-1 infection; however, why this occurs is not known. We hypothesize those changes in cervicovaginal bacteria increase the quantities of these HIV-1 susceptible T-lymphocytes in the cervix, and thereby increase the risk of heterosexual transmission of HIV-1 to females. Through observational studies of well-defined human populations, we will test this hypothesis by using high-throughput DNA sequencing methods, along with advanced microscopy, to comprehensively determine whether menopause results in 1) different kinds of bacteria inhabiting the female reproductive tract; 2) expression of different bacterial genes; and/or 3) modification of cervical gene expression.